Evidence Synthesis: Searching

Developing a comprehensive and effective search strategy is key to a well-defined research question. 

This is an iterative process, which involves continued evaluation and refining.

This search of the evidence is sometimes a balance between precision and sensitivity.

Precision - concepts are clearly and easily defined and the question can be answered with a high degree of certainty:

I only require a small number of recent articles on obesity and quality of life.

Sensitivity - concepts more complex to describe and require gathering many sources of evidence:

I am undertaking a review of the literature

Documenting your search strategies in a clear and transparent way for replicability. 

• • Save searches
  • Search one concept at a time and then combine concepts using the search history
  • Capture search history (excel spreadsheet)
  • Keep a record of the process for transparency and updating

There a number of checklist type tools to assist with reporting and critiquing to ensure clarity, quality control, self-audit and reflective learning for the searching process.

AMSTAR 2: a critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both

CONSORT  - Consolidated Standard of Reporting Trials  The CONSORT-Outcomes 2022 Extension.

Equator network - promotes the transparency and accuracy of reporting health research and the broader use of robust guidelines for reporting.

PRISMA- Preferred Reporting Items for Systematic Reviews and Meta-Analyses. PRISMA-S – Reporting literature searches in systematic reviews.

PRESS - Peer Review of Electronic Search Strategies checklist.

Search summary tables (SST) to determine the effectiveness of search methods for databases and supplementary sources to inform future searching and methods for research in searching.

Bethel AC, Rogers M, Abbott R. (2021) ‘Use of a search summary table to improve systematic review search methods, results, and efficiency’. J Med Libr Assoc., 109(1):97-106.

Rader, T., Mann, M., Stansfield, C., Cooper, C. and Sampson, M. (2014), ‘Methods for documenting systematic review searches: a discussion of common issues’. Res. Syn. Meth., 5: 98-115. https://doi.org/10.1002/jrsm.1097

Build your search terms by:

• Listing keywords you are already familiar with through your own knowledge and experience
• Scanning articles already found through preliminary searches (frequency of terms and controlled vocabulary (Thesaurus, MeSH, Subject Headings)
• What research has already been done?
• Looking for authors publishing in the area or journals associated with the subject area
• Check MIAR (Information Matrix for the Analysis of Journals) to find out in which databases, journals are indexed in and which also includes sources for journal rankings and open access policies
• Using online free text mining tools such as PubmedReminer to check for frequency of words and YaleMeSH Analyser  to help to determine MeSH terms and author generated keywords.

Additionally, think about:

• Spelling variations: (European, American, common misspellings - color, colour)
• Synonyms
• Abbreviations or acronyms
• Former or alternative terms
• Plurals
• Specific index terms in databases (Cinahl - Subject Headings, Medline - MeSH, Thesaurus - PsycINFO)
• Truncation / Wildcard symbols - check the help area in databases.

Building Search Terms.

Supplementary methods for searching such as citation searching, hand searching, web searching, contacting authors or experts and trial register searching are becoming more important.

These methods can add value to identifying study types for reviews as content may not be found by searching only in databases.

The guidance handbooks for methodologies give direction on how to use these methods but further research is needed to determine how these methods actually work and how effective they are.

Further reading:

Cooper, C., Booth, A., Britten, N. et al. (2017) ‘A comparison of results of empirical studies of supplementary search techniques and recommendations in review methodology handbooks: a methodological review’. Syst Rev 6, 234,https://doi.org/10.1186/s13643-017-0625-1.

Some databases will have index terms such as (MeSH, Subject Headings and Thesaurus).

These index terms are controlled vocabulary within databases and when used together with free text keyword searching (title, abstract fields,) will help to focus searches to create more comprehensive and robust search strategies.

Note: there may be a difference in description of an index term across databases, be sure to check the help area of the database.

Use the PRESS checklist to critique your search strategies as they develop

Further reading:

Levay, Paul, Craven Jenny (2019) Systematic searching practical ideas for improving results, Ebook Central.

Building Search Strategies

Finding the Literature 2 (Searching)

Search filters are created to search difficult concepts or concepts which require a number of search terms. 

Saving time and effort –  Overall creation of the search strategy /   Number of records to be screened

Specific types -   Study types such as systematic review/randomised controlled trial /  Topic area

*A number will have been approved for effectiveness, others checked but not approved for preciseness, clarity, precision and sensitivity.

*Search filters not available on all databases, some are particular to a database interface based on the controlled vocabulary and the syntax within that database.

* It is better to assess how a filter might impact on search results before your search is completed.

The ISSG Search Filter Resource